Fiber optics have had a significant impact on many areas of science and technology, not least of which are the areas of physical and chemical sensing. Sensors that measure the intrinsic absorbance, scattering or fluorescence of an analyte are generally referred to as optical sensors. Better analytical selectivity is achieved with a fiber optic chemical sensor (FOCS). The spectroscopic signals obtained with FOCS are the result of specific interactions between the analyte of interest and a reagent phase that is immobilized at the sensing end of the optical fiber. These interactions often take the form of chemical reactions between analyte and reagent that result in a colored or fluorescent product.
Because of their selectivity and versatility with regard to reagent-analyte interactions, FOCS have received much more attention than the optical-type fiber optic sensors. Most reports of FOCS involve the measurement of small molecules (e.g., CO.sub.2, NH.sub.3, metal ions and pH). More recently, FOCS have been applied to the measurement of large macromolecules through the immobilization of highly selective bioreceptor affinity reagent phases.
In certain prior art, the reagent phase of a FOCS has been immobilized by covalent attachment to the fiber surface, entrapped in a membrane sealed compartment, or incorporated into a polymer matrix at the distal end of the optical fiber.
These configurations allowed a highly sensitive and selective analysis of chemicals in biological fluids such as blood and other body fluids. These analyses, although selective and sensitive, may only be performed once before regeneration of the reagent was required. This regeneration was time consuming and required the removal of the sensor from the biological fluid.
It is therefore an object of the present invention to provide a regenerable, i.e. semi-continuous, fiber optic-based sensor.
It is another object of the present invention to provide a regenerable fiber optic-based sensor useful in in situ analyses.
It is another object of the present invention to provide a regenerable fiber optic-based sensor small enough to be placed into a biological system, e.g., through a hypodermic needle.